Currently for outdoor lighting, numerous types of luminaires exist. They differ not only in style but especially with respect to the illumination pattern. For example, sidewalks require long, narrow illumination patterns while traffic intersections require broader, wide area illumination patterns. Within the lighting industry there exists a number of standardized illumination patterns referred to as Type I, Type II, Type III, Type IV, etc.
Designers and installers of luminaires are required to specify, stock, supply and install many different luminaire types in order to achieve the required illumination pattern. More problematic are cases where local geography requires customized illumination patterns not easily met by standardized luminaire types.